This application relates to multi-circuit refrigerant systems that are capable of executing multiple modes of operation. Typically, these systems have a reheat coil(s) incorporated into the system design to provide a reheat function, and additional control means capable of alternating between operational regimes independently for each circuit in response to environmental conditions and load demands.
Refrigerant cycles are utilized to control the temperature and humidity of air in various environments to be conditioned. Typically, a refrigerant is compressed in a compressor and delivered to a condenser. In the condenser, heat is exchanged between outside ambient air and the refrigerant. From the condenser, the refrigerant passes to an expansion device in which the refrigerant is expanded to a lower pressure and temperature, and then to an evaporator. In the evaporator, heat is exchanged between the refrigerant and the indoor air, to condition the indoor air. When the refrigerant cycle is in operation, an evaporator cools, the air that is being supplied to the indoor environment. In addition, as the temperature of the indoor air is lowered, moisture usually is also taken out of the air. In this manner, the humidity level of the indoor air can also be controlled.
In some cases, the temperature level, to which the air is brought to provide comfort environment in the conditioned space, may need to be higher than the temperature that would provide the ideal humidity level. Such corresponding levels of temperature and humidity may vary from one application to another and are highly dependent on environmental and operating conditions. This has presented design challenges to refrigerant cycle designers. One way to address such challenges is to utilize reheat coils. In many cases, the reheat coils placed in the path of the indoor air stream, behind the evaporator, are employed for the purpose of reheating the air supplied to the conditioned space after it has been overcooled in the evaporator for moisture removal.
Multi-circuit refrigerant systems are also applied in the industry, wherein separate compressors and heat exchangers operate under a single control to provide various levels of sensible and latent capacity in response to the load demands and wherein each circuit can independently function in one of several operational regimes.
A further option available to a refrigerant system designer is to integrate a reheat coil(s) in the schematics for some of the refrigerant circuits of a multi-circuit system. As known, in a reheat coil, at least a portion of the refrigerant upstream of the expansion device is passed through a reheat heat exchanger and then is returned back to the main circuit, and at least a portion of the conditioned air having passed over the evaporator is then passed over this reheat heat exchanger to be reheated to a desired temperature. Although these multi-circuit systems have been known to incorporate a reheat coil into one or more of the circuits, these circuits and their reheat functions have always been independent or functionally separated (discrete) and they have not had any interaction or communication with each other. Moreover, reheat concepts for each circuit were always identical within the system in the principal of their design and operation.